4. Whisk together eggs and buttermillk. Add egg mixture to pumpkin mixture and whisk to combine. Fold mixture into pumpkin mixture until combined (some small lumps of flour are OK). Fold walnuts, if using, into batter. Scrape batter into prepared pans. Sprinkle topping evenly over top of each loaf. Bake until skewer inserted in center of loaf comes out clean, 45 to 50 minutes. Let breads cool in pans on wire rack for 20 minutes. Remove breads from pans and let cool for at least 1.5 hours. Serve warm or at room temperature.